Embodiments of the invention relate to data transmission to and from down hole equipment and in particular, though not exclusively, to a data communication system and a method of data transmission through a sucker rod string between the sub-surface and a surface location of a well bore.
In the exploration and production of oil and gas wells, well bores are drilled from the surface to a subsurface location to access the reserves. The well bore is typically ‘cased’ with tubing to prevent collapse. A string can be run into the well bore to position down hole equipment at a sub-surface location. Down hole equipment is understood to refer to any tool, equipment or instrument that is used in a well bore.
Data needs to be transmitted between down hole equipment and the surface for various reasons. For example, monitoring performance of motors/pumps; transmission of control signals for control of valves; measuring device orientation and position, and making physical measurements. Power may also need to be transmitted to the down hole monitoring equipment. Due to the complexity of construction and the depths which wells are drilled, the data is sent to surface without installing dedicated cables and power for the down hole instrumentation is also sent without adding wires to the well equipment.
Telemetry systems are known which use the casing to transmit electromagnetic and acoustic data signals from a sub-surface location to a surface location. Such systems typically cannot achieve transmission of power from surface to sub-surface.
An embodiment of the present invention provides an alternative wireless system and method of data transmission when an electrical cable is not present in the well bore. In an embodiment of the present invention an alternative system and method of power transfer is also described.